Cryosurgical probes have been selectively used in the treatment of a variety of diseases. Functionally, cryosurgical probes have the capability of reducing the temperature of a targeted body tissue to thereby destroy, remove and/or inactivate the tissue. Because of this ability, the use of cryothermal treatment has been prescribed in the treatment of various cancers, including breast cancer and prostate cancer, as well as to remove various tumors, cysts and in the treatment of cataracts. More recently, the use of cryothermal treatment has been shown to be effective in destroying specific conductive tissues of the heart. This technique can be used to block abnormal electrical signals as a treatment for various heart arrhythmias such as atrial fibrillation.
In a typical cryoprobe procedure, the tip of the probe is cooled by a cryo-fluid (e.g. Nitrous Oxide) and the cooled tip is placed in contact with the tissue. This contact causes heat to flow from the tissue and into the probe tip. Because the heat transfer rate is proportional to the contact area between the tissue and probe, it is generally desirable to contact as much of the target tissue as possible. However, in most procedures, the exposed surface of the target tissue is contoured and this contour often precludes the establishment of large or extended contact areas when using a conventional cylindrical probe.
Typically, the exact contour of the target tissue is only known after an internal organ, such as the heart, has been exposed. Once an internal organ such as the heart has been exposed, the procedure must be performed quickly to minimize trauma to the patient. With a standard cylindrical probe tip, multiple contacts are often required to cryoablate even a mildly contoured target tissue. This requirement of multiple contacts is time consuming and can present an increased risk to the patient due to the lengthy duration of the procedure. In addition, the use of multiple contacts can often result in the non-uniform ablation of tissue that can undermine the success of the procedure.
Another case in which a standard cylindrical probe may be inadequate is when the target tissue cannot be adequately exposed for contact with the conventional cylindrical probe. In still other cases, adequate exposure for contact with a conventional cylindrical probe may be possible, but an unreasonable amount of time may be required to effect such an exposure. On the other hand, a probe tip that is reshapeable may be able to access tissue that is otherwise inaccessible or hard to access with a conventional cylindrical probe.
In addition to having an adequate contact area between the probe and tissue, proper heat transfer requires that an unimpeded flow of refrigerant pass through the probe tip. With this in mind, refrigerant flow is an important factor that must be considered when contemplating the reconfiguration of a probe tip to conform with a contoured target tissue.
In light of the above, it is an object of the present invention to provide devices and methods suitable for the purposes of cryoablating exposed tissue in cases where the surface of the exposed tissue is contoured. It is another object of the present invention to provide a tip for a cryoprobe that can be quickly reshaped to conform to the surface of a contoured target tissue, allowing the tip to be reshaped after the target tissue has been exposed. It is yet another object of the present invention to provide a tip for a cryoprobe that can be quickly reshaped with minimal interference to the flow of refrigerant through the tip. Yet another object of the present invention is to provide a reshapeable tip for a cryoprobe and a method for its use that is relatively easy to implement and comparatively cost effective.